Fix small typo in python3 docs
Fix small typo in python3 docs

Add missing 'be'
adrianmoisey/cptdevops,pallets/flask,pallets/flask,fkazimierczak/flask,drewja/flask,Endika/flask,pallets/flask,mitsuhiko/flask,auready/flask,fkazimierczak/flask,drewja/flask,Endika/flask,dawran6/flask,auready/flask,tristanfisher/flask,drewja/flask,adrianmoisey/cptdevops,mitsuhiko/flask,fkazimierczak/flask,tristanfisher/flask,dawran6/flask